In machines with rotary drive, it is important that the drive-side shaft aligns as precisely as possible with the driven-side shaft, i.e., that their rotation axes ideally coincide. However, this is practically never achieved in practice. Alignment errors can arise, whether in the form of displacement, i.e., the rotation axes are parallel, but do not correspond, or angular displacement, i.e., the rotation axes are angled relative to each other (angular error). In practice, both errors are most often encountered in combination. The goal is to minimize the latter to thereby keep the radial and axial forces they induce in the bearings as small as possible, so as to protect bearings, gaskets and couplings.
In practice, alignment between the drive shaft of the motor and drive shaft of a machine takes place with the machine standing idle, even though this is disadvantageous for system-related reasons. The machine is only exposed to static influences when standing idle, but during operation is subject to dynamic influences, which can be many times higher. In addition, cracked bearings are positioned differently during operation than when standing idle.